EXTRAPYRAMIDAL SYSTEM

KINNARI THACKER

ROLL NO:132

INTRODUCTION

• THE MOTOR PATHWAYS ARE THE DESCENDING TRACTS.

• INCLUDES TWO MAIN TRACTS:i. PYRAMIDAL TRACTS.ii. EXTRAPYRAMIDAL TRACTS.

EXTRAPYRAMIDAL TRACTS

• DESCENDING TRACTS OTHER THAN PYRAMIDAL TRACTS IN THE SPINAL CORD ARE COLLECTIVELY CALLED EXTRAPYRAMIDAL TRACTS.

CONT…

• INCLUDES:i. RUBROSPINAL TRACT.ii. TECTOSPINAL TRACT.iii. VESTIBULOSPINAL TRACT.iv. RETICULOSPINAL TRACT.v. MEDIAL LONGITUDINAL FASCICULUS.

RUBROSPINAL TRACT• ORIGIN: RED NUCLEUS OF MIDBRAIN.• COURSE: IMMEDIATELY AFTER ORIGIN THESE

FIBRES CROSS TO THE OPPOSITE SIDE--> DESCENDS THROUGH PONS AND MEDULLA .

• TERMINATION: MAINLY ON THE INTERNEURONS.

CONT…• FUNCTION: - EXHIBITS FACILITATORY INFLUENCE ON FLEXOR MUSCLES AND

INHIBITORY INFLUENCE ON THE EXTENSORS.

VESTIBULOSPINAL TRACTS

• THERE ARE TWO VESTIBULOSPINAL TRACTS:i. LATERAL VESTIBULOSPINAL TRACTii. MEDIAL VESTIBULOSPINAL TRACT

LATERAL VESTIBULOSPINAL TRACT

• ORIGIN: LATERAL VESTIBULAR NUCLEUS.• COURSE: THESE FIBRES ARE UNCROSSED AND

LIES IN THE ANTERIOR FUNICULUS OF SPINAL CORD SHIFTING MEDIALLY AS IT DESCENDS.

• TERMINATION: EXTEND UPTO CAUDAL SEGMENTS OF CORD AND TERMINATE INTO NEURONS OF VENTRAL GREY COLUMN.

CONT….• FUNCTIONS:- MAINLY FACILITATES

ACTIVITY OF EXTENSOR MUSCLES AND INHIBITS THE ACTIVITY OF FLEXOR MUSCLES IN

ASSOCIATION WITH THE MAINTENANCE OF

BALANCE.

MEDIAL VESTIBULOSPINAL TRACT

• ORIGIN: MEDIAL VESTIBULAR NUCLEUS.• COURSE: DESCENDS THROUGH THE ANTERIOR

FUNICULUS.• TERMINATION: END IN THE ANTERIOR MOTOR

NEURONS DIRECTLY OR THROUGH INTERNUNCIAL NEURONS OF CERVICAL SEGMENTS OF SPINAL CORD.

CONT…• FUNCTION:- DONOR CONNECTION OF

MEDIAL LONGITUDINAL FASCICULUS.

- PROVIDES A REFLEX PATHWAY FOR MOVEMENTS OF HEAD, NECK, AND EYES IN RESPONSE TO VISUAL AND AUDITORY STIMULI.

RETICULOSPINAL TRACT

• THRE ARE TWO RETICULOSPINAL TRACTS:i. MEDIAL(PONTINE) RETICULOSPINAL TRACT.ii. LATERAL(MEDULLARY) RETICULOSPINAL

TRACT.

MEDIAL RETICULOSPINAL TRACT

• ORIGIN: MEDIAL PONTINE RETICULAR FORMATION.

• COURSE: ANTERIOR FUNICULUS OF SPINAL CORD

• TERMINATION: IN THE LAMINA OF SPINAL GREY MATTER AND THROUGH INTERNUNCIAL NEURONS INFLUENCE ALPHA AND GAMMA NEURONS

CONT…• FUNCTIONS:- EXCITATORY TO

ANTIGRAVITY MUSCLES- FACILITATE CONTROL OF

VOLUNTARY AND REFLEX MOVEMENTS AND CONTROL OF MUSCLE TONE

- FAVOURS EXPIRATION- VASOCONSTRICTION

LATERAL RETICULOSPINAL

• ORIGIN: MEDULLARY RETICULAR FORMATION.• COURSE: DESCENDS IN LATERAL FUNICULUS

MEDIAL TO LATERAL CORTICOSPINAL AND RUBROSPINAL TRACTS.

• TERMINATION: INTERNUNCIAL NEURONS OF LAMINAE OF SPINAL CORD.

CONT…• FUNCTIONS:- INHIBITORY TO

ANTIGRAVITY MUSCLES.- INHIBIT CONTROL OF

VOLUNTARY AND REFLEX MOVEMENTS AND MUSCLE TONE.

- FAVOURS INSPIRATION.- VASODILATATION.

TECTOSPINAL TRACT

• ORIGIN: SUPERIOR COLLICULUS• COURSE: DESCENDS THROUGH PONS AND

MEDULLA INTO THE ANTERIOR WHITE FUNICULUS OF THE SPINAL CORD

• TERMINATION: UPPER CERVICAL LEVELS BY SYNAPSING ON THE ANTERIOR HORN CELL.

CONT…• FUNCTION:- MOTOR LIMB OF THE

REFLEX PATHWAY IN RESPONSE TO VISUAL, HEARING OR OTHER EXTEROCEPTIVE STIMULI.

MEDIAL LONGITUDINAL FASCICULUS

• ORIGIN: MEDIAL VESTIBULAR NUCLEUS RETICULAR FORMATION SUPERIOR COLLICULUS INTERSTITIAL NUCLEUS CAJAL• COURSE: DESCENDS UPTO UPPER CERVICAL

REGION.• TERMINATION: VENTRAL HORN CELLS THAT

INNERVATE MUSCLE OF THE NECK.

CONT…

• FUNCTION:- COORDINATION OF

REFLEX OCULAR MOVEMENTS

- INTEGRATION OF EYE AND NECK MOVEMENTS.